LANCASTER — It was at the machines used for grinding and mixing gunpowder components that things went wrong just after lunch on May 14, 2010, killing two workers at a Colebrook plant and leading to the arrest of their employer.

Jurors became more familiar with the process used and the machinery required to make gunpowder, as the manslaughter and negligent homicide trial of Craig Sanborn continued Thursday.

An initial explosion set off several secondary explosions that May day. When the resulting fire was extinguished, investigators found the bodies of two men whose job it had been to run the machines; Donald Kendall, 56, of Colebrook, and Jesse Kennett, 49, of Stratford.The initial blast in the plant at 23 Gould St. was so powerful that the large industrial machines produced by General Dynamics were left misshapen.

One, in particular, was “severely deformed,” Robert Zalosh, who’s knowledgeable in combustible dust hazards, told the nine women and five men, including two alternates, who comprise the jury.

Also listening were Judge Peter H. Bornstein and Sanborn, of Maidstone, Vt., the plant’s former owner. The state has accused Sanborn of being negligent and reckless in failing to take proper precautions, including not protecting his employees from injury, when he set up and began running his Black Mag plant.

The 64-year-old Sanborn faces a potentially long term in New Hampshire State Prison should the jury convict him.

Under questioning by prosecutor John McCormick, Zalosh said even with proper precautions and safeguards, including placing sandbag bunkers around the machines to separate them from one another, the manufacture of gunpowder is an “inherently dangerous” process.

Defense attorney Mark Sisti quickly established that Zalosh did not profess to be an expert in gunpowder production. And as he had with previous witnesses, Sisti pressed the point that no investigators including Zalosh — who said he examined the scene four or five days after the blast — were able to establish what triggered the explosion.